Growth of thin films of the defect perovskite LaCuO[sub 3[minus][delta]] by pulsed laser deposition

Oriented thin films of the defect perovskite LaCuO[sub 3[minus][delta]] (LCO) have been grown on (100) SrTiO[sub 3] substrates by pulsed laser deposition. The orthorhombic, oxygen-deficient La[sub 2]Cu[sub 2]O[sub 5] ([delta] = 0.5) phase, which is the end-member of the perovskite series, is formed at a growth temperature of 700[degrees]C under 200 mTorr background O[sub 2] pressure. With additional oxygen uptake during cooldown, the orthorhombic phase can be easily converted to the monoclinic modification ([delta] [approx lt] 0.4). The more highly oxygenated tetragonal phase ([delta] [approx lt] 0.2) is, however, not obtained for background O[sub 2] pressures up to 760 Torr. Partial conversion to the tetragonal phase has been achieved by postannealing the films at 600-650[degrees]C under high oxygen pressure (450 bar). From resistivity measurements, a distinct insulator-metal transition is observed in going from the orthorhombic to the monoclinic structure, with postannealed films containing the mixed tetragonal and monoclinic phases showing the lowest resistivity. However, no evidence of superconductivity has been detected in any of the films down to 5 K.